5. Drying process and requirements
In the production of tinplate printing, the drying of ink is a complex physical and chemical reaction process. To properly control the drying speed of the ink and master the physical and chemical mechanism in the drying of the ink, it is possible to effectively carry out rapid printing operations and ensure product quality. Drying the ink too fast will reduce the normal transfer performance of the ink, affecting the normal production; causing the print to be faint, the ink color is light, the ink on the surface of the printing plate and the ink roller is dry, and the ink in the transfer is blocked; The layer is outwardly expanded; if the amount of the desiccant is too large, the ink adsorption property is increased, and the blank portion is dirty. The drying of the ink is too slow, which may cause difficulty in overprinting, adhesion, adhesion, etc., and the degree of firmness is lowered; it is easy to cause scratches during the conveyance process. Therefore, the drying speed of the ink should be suitable, too fast and too slow are unfavorable.
The drying process is determined by three factors:
A, the temperature set by the oven, B, the time to maintain the peak temperature, C, the temperature curve of the drying room
The drying room usually consists of three parts: a heating zone, a constant temperature zone, and a cooling zone. The main function of the warming zone is to raise the iron piece from room temperature to the set temperature. The main function of the constant temperature zone is to maintain the temperature reached by the heating zone. The function of the cooling zone is to fully cool the dried iron sheet if cooled. Not enough, the paint film is easy to scratch when the iron sheet is collected, and the adhesive sheet is likely to occur after stacking.
The peak temperature time is kept too short, and the coating or ink is not sufficiently baked, which may cause the ink and paint to become soft and not fully exert its protection or other functions. After the high temperature cooking test, adhesion often occurs. If the peak temperature time is kept too long, the baking will be excessive, the coating will become brittle, and it will be easily broken during processing. Excessive baking will cause the color of the paint and ink to turn yellow.
In order to avoid inadequate baking and excessive baking, the oven temperature profile must be checked regularly to determine the peak temperature time at standard machine speed.